CalculateResolution v1¶

CalculateResolution dialog.

Table of Contents

Summary
Properties
Description
- Beam Divergence
Usage
Source

Summary ¶

Calculates the reflectometry resolution (dQ/Q) for a given workspace.

Properties ¶

Name	Direction	Type	Default	Description
Workspace	Input	MatrixWorkspace	Mandatory	Workspace to calculate the instrument resolution of.
TwoTheta	Input	number	Optional	Two theta scattering angle in degrees.
FirstSlitName	Input	string	slit1	Component name of the first slit.
SecondSlitName	Input	string	slit2	Component name of the second slit.
VerticalGapParameter	Input	string	vertical gap	Parameter the vertical gap of each slit can be found in.
TwoThetaLogName	Input	string	Theta	Name two theta can be found in the run log as.
Resolution	Output	number		Calculated resolution (dq/q).
TwoThetaOut	Output	number		Two theta scattering angle in degrees.

This algorithm takes a workspace and a value for two theta, and attempts to calculate the reflectometry resolution (dQ/Q) from them. If no value is provided for two theta then CalculateResolution will attempt to fetch a value from the workspace’s log using the two theta log name provided.

CalculateResolution outputs two values, the calculated resolution and the value of TwoTheta that was used in the calculation. The latter is useful when TwoTheta was not given to CalculateResolution, causing CalculateResolution to extract it from the workspace’s sample log.

The effective inverse of this algorithm is CalculateSlits v1.

Beam Divergence ¶

Schematic showing beam divergence using two slits (Slit1 and Slit2)

Proof

$\frac{d1}{x} \equiv \frac{d2}{l - x} \equiv tan\alpha \therefore \frac{d1}{x} = \frac{d1 + d2}{l} \therefore \alpha = tan^{-1}\left(\frac{d1 + d2}{l}\right)$

where $\alpha$ gives is the beam divergence in radians. Parameter d1 is the vertical distance of Slit1 opening, d2 is the same for Slit2. parameter l is the distance between the slits in the beam direction. See figure above for reference.

Usage ¶

ws = Load('INTER00013460')
res, two_theta = CalculateResolution(Workspace = ws, TwoTheta = 0.7)
print("Resolution: %.4f" % res)
print("Two Theta: %.4f" % two_theta)